1. Field
An air conditioner and a method of controlling an air conditioner are disclosed herein.
2. Background
Air conditioners are appliances that maintain air within a predetermined space in a most proper state according to a use and purpose thereof. In general, such an air conditioner may include a compressor, a condenser, an expansion device, and evaporator. Thus, the air conditioner has a refrigerant cycle in which compression, condensation, expansion, and evaporation processes of a refrigerant are performed. Thus, the air conditioner may heat or cool the predetermined space.
The predetermined space may be variously provided according to a place at which the air conditioner is used. For example, when the air conditioner is disposed in a home or office, the predetermined space may be an indoor space of a house or building. On the other hand, when the air conditioner is disposed in a vehicle, the predetermined space may be a space in which a person rides.
When the air conditioner performs a cooling operation, an outdoor heat-exchanger provided in an outdoor unit or device may serve as a condenser, and an indoor heat-exchanger provided in an indoor unit or device may serve as an evaporator. On the other hand, when the air conditioner performs a heating operation, the indoor heat-exchanger may serve as the condenser, and the outdoor heat-exchanger may serve as the evaporator.
In general, an air conditioner may include a compressor, a gas/liquid separator to separate a gaseous refrigerant to introduce the separated gaseous refrigerant into the compressor, a flow switching part or switch to switch a flow direction of the high-pressure refrigerant discharged from the compressor, and outdoor and indoor heat-exchangers. When the air conditioner performs a cooling operation, the refrigerant compressed in the compressor may be introduced into the outdoor heat-exchanger via the flow switching part. Then, the refrigerant condensed in the outdoor heat-exchanger may be decompressed in an expansion device and evaporated in the indoor heat-exchanger.
When the air conditioner performs a heating operation, the refrigerant compressed in the compressor may be introduced into the indoor heat-exchanger via the flow switching part. Then, the refrigerant condensed in the indoor heat-exchanger may be decompressed in an expansion device and evaporated in the outdoor heat-exchanger.
When the air conditioner performs the cooling or heating operation, the refrigerant compressed in the compressor may generally have a pressure (high pressure) within a predetermined range. However, the high pressure may rise to an abnormal range during operation. For example, if external air changes in temperature, or an amount of refrigerant circulating in the cycle is not suitable, the high pressure may rise.
Also, in a case of the heating operation, a time taken to allow the refrigerant discharged from the compressor to circulate according to a length of a tube may increase when a system initially operates. Thus, a pressure of a compressor suction inlet may be significantly lowered. Also, due to the above-described limitations, an oil forming phenomenon may occur within the compressor, or the compressor may operate out of an operable range thereof, deteriorating reliability.
To solve the above-described limitations, if the high pressure rises, the compressor according to the related art operates at a lowest frequency. In detail, the air conditioner according to the related art performs the cooling or heating operation, a target high-pressure or a target low-pressure of the compressor may be initially set, and an operation high-pressure or low-pressure of the operating compressor detected.
The detected operation high-pressure or operation low-pressure and the set target high-pressure or target low-pressure may be compared to each other to determine an operation state of the compressor. That is, it is determined whether the operation high-pressure detected by a high-pressure sensor is above the target high-pressure and whether the operation low-pressure detected by a low-pressure sensor is below the target low-pressure.
If it is determined that the detected operation high-pressure is below the target high-pressure, or the operation low-pressure is above the target low-pressure, the target high-pressure and the target low-pressure may be changed and reset. That is, when a difference between the operation high-pressure and the operation low-pressure is less than a difference between the target high-pressure and the target low-pressure, the target pressure may be reset so that an operation pressure corresponding to an indoor load is generated. On the other hand, when it is determined that the detected operation high-pressure is above the target high-pressure, or the operation low-pressure is below the target low-pressure, the compressor may be variably controlled to allow the operation low-pressure to reach the target low-pressure.
That is, according to the related art, the operation high-pressure or low-pressure of the air conditioner may be detected, and the detected operation high-pressure or operation low-pressure may be compared to the initially set target high-pressure or target low-pressure to change a target value so that a difference between the high-pressure and the low-pressure belongs to a predetermined range to prevent the difference between the operation pressure and the target pressure from being excessive, thereby allowing a protection operation for the compressor to be performed.
As a result, operation of the compressor may be controllable on the basis of operation frequency in the related art. More particularly, the compressor may operate at a lowest frequency during the low load operation to control an operation factor.
However, when the compressor operates at the lowest frequency, a lowest amount of refrigerant previously set in the system has to be maintained. Thus, the lowest frequency operation performance of the compressor may be high, and thus, operation efficiency may be deteriorated. That is, according to the related art, there is a limitation that it is difficult to efficiently control the operation of the air conditioner under the low load condition.